The Callisto annotation tool was developed to support linguistic annotation of textual sources for any Unicode-supported language. The initial development of the tool by the MITRE Corporation was funded by the U. S. government. The primary development team consisted of Chad McHenry, Robyn Kozierok, and Laurel Riek, with contributions from David Day. Design and interface guidance was provided by Lisa Ferro, Janet Hitzeman, Marcia Lazo, Marc Vilain and David Day. The project lead for this effort was David Day.